The present invention relates generally to mobile communications system, and more specifically to vehicular power booster circuitry for a duplex multi-level portable radio transceiver.
A mobile radio transceiver as shown and described in U.S. Pat. No. 4,636,741 has a portable radio transceiver and a vehicular adaptor having an antenna. When the portable transceiver is used in the vehicle, it is coupled to the adaptor to enable it to amplify the signal from the transceiver and transmit it from the antenna of the adaptor, instead of from the antenna of the transceiver. When the transceiver is used outside of the vehicle, it is disconnected from the adaptor and operates on a built-in battery to transmit signals from the transceiver antenna. A power control driver is provided in the transceiver unit to set its output power at one of several predetermined power levels. When the transceiver is operated on the adaptor mode for boosting power, the power level established in the transceiver is communicated to the adaptor in the form of an encoded signal. Therefore, the adaptor must be provided with a costly decoding circuit to receive the power level identification code to set the booster power level corresponding to the level set by the transceiver. Since the prior art transceiver has an antenna of its own and can generate sufficient power for direct transmission from the antenna, it can be used with a high degree of freedom outside of the vehicle. However, the circuitry for generating the necessary power for direct transmission from the transceiver occupies extra space and adds to its weight. It may be desirable that the transceiver be less bulky and unwieldy for use inside of the vehicle if there is no need to use it outside of the vehicle with the flexibility of the prior art.